20818639 has 8 divisors (see below), whose sum is σ = 21548160. Its totient is φ = 20092800.

The previous prime is 20818621. The next prime is 20818643. The reversal of 20818639 is 93681802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20818639 - 2¹⁵ = 20785871 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20818598 and 20818607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20818649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15507 + ... + 16795.

It is an arithmetic number, because the mean of its divisors is an integer number (2693520).

Almost surely, 2^20818639 is an apocalyptic number.

20818639 is a deficient number, since it is larger than the sum of its proper divisors (729521).

20818639 is a wasteful number, since it uses less digits than its factorization.

20818639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1841.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 20818639 is about 4562.7446783707. The cubic root of 20818639 is about 275.0958960325.

The spelling of 20818639 in words is "twenty million, eight hundred eighteen thousand, six hundred thirty-nine".